Field of Endeavor
This disclosure relates to a polyethylene sealant film having high tensile strength properties and excellent resistance to impact breakage, and a package using the same.
Brief Description of the Related Art
Polyethylene sealant films are frequently used as packaging materials, being excellent in strength properties, heat sealability, heat resistance, and cold resistance.
However, while the polyethylene sealant films are excellent in strength properties, the films are broken by excessive impact to damage sealability as a package. A most effective means to impart a sufficient impact resistance is to increase the film thickness, but this is a problem because of increasing cost of the package.
As a measure, it is known to improve the impact resistance by stretching to orient the film. On the other hand, this has a problem of inferiority in heat sealability, and therefore it is difficult to develop the technique for the use as a sealant.
Although various devices have been made in order to improve the impact resistance of polyethylene sealant films as is, they have still problems in being put to practical use.
JP 2004-167956 A discloses a laminate formed of a substrate film and a sealant layer composed of two layers laminated thereto. One of the sealant layer composed of two layers is made of a general linear low density polyethylene resin or a linear low density polyethylene resin produced by the polymerization using a metallocene-based single site catalyst located on the laminating side, and the other is made of a linear low density polyethylene resin produced by the polymerization using a metallocene-based single site catalyst or a general linear low density polyethylene which contacts the contents. The purpose of the laminate is to prevent blocking, and is characterized by providing many convexes on the surface of the sealant layer.
JP 2006-181831 A discloses a multilayer polyethylene sealant film wherein a heat fusion layer made of ethylene-α-olefin random copolymer is laminated onto the adjacent face of a biaxially stretched ethylene polymer film substrate layer. The film is characterized by easy tearability with excellent transparency, shrinkability, heat sealability, and flexing resistance.